Rock has the best single-type coverage in the game, but that's pretty much its only upside. It has too many weaknesses to overall be viable. There's a reason that there are 16 NU Rock types and only 11 (counting Arceus) in higher tiers.
Outside of Tyranitar and Terrakion (both excellent due to typing, ability and stats), you have a couple okay options. Aerodactyl makes a good support Pokemon with 130 Speed. All offensive Rock-types can either use Rock Polish or Shell Smash. Shuckle is infamous for its defenses and total lack of willingness to die. Cradily runs a mean Curse set and can use Storm Drain (DW) to absorb Water attacks that plague Sandstorm teams. Archeops can just beat everything to a pulp with Acrobatics, but frailty and Defeatist let it down. Armaldo (DW), Kabutops, Omastar, and Carracosta (DW) get Swift Swim, although Armaldo doesn't really need it and the latter two use Shell Smash instead. Lunatone and Solrock can use Baton Pass if you want them to (Pokemon XD purification move).
Moral of the story: You can make Rock-types work if you try, but there are usually better options.